CFD modelling of electric vehicle fire suppression: Avoiding flame spread using sprinklers in a well-ventilated underground parking
This study investigates the effectiveness of water-based sprinkler systems in mitigating fire spread from electric vehicle (EV) battery thermal runaway events in an underground parking garage (9.5 m × 16 m) using Fire Dynamics Simulator (FDS v6.9.1). A series of three-dimensional CFD simulations were conducted to evaluate how different sprinkler configurations influence heat release rate (HRR) and fire propagation between an initiating EV and two adjacent vehicles.
The study is contextualized by a thorough literature review on lithium-ion battery chemistry, the mechanics of thermal runaway (TR) and the characteristics of an EV fire. This theoretical foundation was used to establish a worst-case scenario for simulation, specifically selecting a 100% State of Charge (SOC) to reflect the highest potential for fire intensity and rapid fire growth. While the literature identifies significant risks regarding toxic gas emissions (such as hydrogen fluoride) and vapor cloud explosions (VCE), these phenomena were intentionally excluded from the numerical scope. This decision was made because these hazards are either not the primary drivers of vehicle-to-vehicle fire spread or cannot be modeled with sufficient accuracy within the constraints of FDS, which is a low-Mach-number solver.
10 cm computational grid, validated through sensitivity analysis, was used to balance accuracy and computational cost. Seven sprinkler scenarios were tested, varying activation (temperature), orientation, and discharge intensity.
Results show that an unconstrained fire scenario produces a peak HRR exceeding 18 MW due to multi-vehicle involvement. Sprinkler systems significantly reduce fire severity and stop or limit the fire spread, achieving up to an 82% reduction in peak HRR for standard ceiling-mounted systems (6.7 L/min) and up to 93% for high-intensity configurations. Although the FDS model shows that high-velocity jet flames are more buoyancy-dominated than in reality due to the neglect of pressure-driven expansion, the model successfully captures the critical interaction between water application and thermal exposure. These high-velocity jet flames, however, are only marginally affected by sprinkler discharge in the simulations; they are not the primary driver of vehicle-to-vehicle fire spread. Instead, fire propagation is driven by sustained thermal exposure leading to window failure and ignition of interior combustibles.
The results demonstrate that water-based sprinkler systems are effective in limiting large-scale EV fire propagation in enclosed parking structures, despite their inability to suppress thermal runaway at the battery cell level.
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